CAS CH 131 Study Guide - Final Guide: Exothermic Reaction, Endothermic Process, Heat Capacity

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6 Feb 2014

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Work done by system means w is negative. (work is leaving the system) Work done by surroundings means w is positive. A gas is heated inside of a balloon with frictionless expansion. 5 l to 5. 7 l. the pressure inside the balloon and surroundings is 2. 1 atm. W = -p v = -2. 1(5. 7-5) = -1. 47 j. Adding heat would make sure there is still the same internal energy. Temperature of the water at the top was measured along with the bottom. Ep = 0. 15 kg (9. 8) (-100) = -147 j. Q = 150 g (4. 18) t = 147. A 61 g hot piece of metal at 120oc is in 100 g of water at 20oc. The metal cools and the water heats up until they are both at a temperature of 26. 39oc. Q of metal = q of water. (61 g)(cs)(26. 39-120) = 100 g (4. 18)(26. 39 - 20)

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Energy cannot be created nor destroyed, but it can be transferred between a reaction and its surroundings. The change in energy, Delta E, is positive if the reaction absorbs energy, and it is negative if the reaction releases energy. You may also see this expressed in terms of change in internal energy, Delta U. For the purposes of this question, Delta U and Delta E are equal. One way a reaction can transfer energy to or from the surroundings is by releasing or absorbing heat. A reaction can also transfer energy, in the form of work, through a change in volume. The total change in energy is the sum of the heat and work: Delta E = q + w At constant pressure, q = Delta H and w = -P Delta V and so Delta E = Delta H - P Delta V Assuming constant pressure, rank these reactions from most energy released by the system to most energy absorbed by the system, based on the following descriptions: Surroundings get colder and the system decreases in volume. Surroundings get hotter and the system expands in volume. Surroundings get hotter and the system decreases in volume. Surroundings get hotter and the system does not change in volume. Also assume that the magnitude of the volume and temperature changes are similar among the reactions. Rank from most energy released to most energy absorbed. To rank items as equivalent, overlap them. Energy cannot be created nor destroyed, but it can be transferred between a reaction and its surroundings. The change in energy, Delta E, is positive if the reaction absorbs energy, and it is negative if the reaction releases energy. You may also see this expressed in terms of change in internal energy, Delta U. For the purposes of this question, Delta U and Delta E are equal. One way a reaction can transfer energy to or from the surroundings is by releasing or absorbing heat. A reaction can also transfer energy, in the form of work, through a change in volume. The total change in energy is the sum of the heat and work: Delta E = q + w At constant pressure, q = Delta H and w = -P Delta V and so Delta E = Delta H - P Delta V A mole of X reacts at a constant pressure of 43.0 atm via the reaction X(g) + 4Y(g) - 2Z(g), Delta H degree = -75.0 kJ Before the reaction, the volume of the gaseous mixture was 5.00 L. After the reaction, the volume was 2.00 L Calculate the value of the total energy change. AE, in kilojoules. Express your answer with the appropriate units.

3. Enthalpy change is defined as __________ a. the energy that is transferred into or out of a system when the pressure is constant and only PâV work is done. b. the change in internal energy of a system when the pressure is constant. c. the change in internal energy of a system when the volume is constant. d. the energy that is transferred into or out of a system when the pressure is constant and no work is done. e. the change in internal energy of a system when the pressure is constant and no work is done.

4. In an experiment, 0.250 kg water at 95.0Â°C is quickly transferred to a 0.500 kg alumina crucible at 25Â°C. The final temperature comes to 61.8Â°C. What is the approximate specific heat capacity of alumina? [cp(water) = 4.18 J/(g ï Â°C)] a. 7.94 J/(g ï Â°C) d. 0.664 J/(g ï Â°C) b. 5.17 J/(g ï Â°C) e. 2.32 J/(g ï Â°C) c. 1.89 J/(g ï Â°C)

5. When a 13.0 g sample of NaOH(s) dissolves in 400.0 mL of water to produce 413.0 g of solution in a constant pressure calorimeter, the temperature of the water and reaction vessel changes from 22.6Â°C to 30.6Â°C. Assume that the specific heat capacity of the solution is 4.2 J/(g ï Â°C), and that the heat capacity of the reaction vessel is 1.00 J/Â°C. What is the molar enthalpy of solution of the sodium hydroxide (40.00 g/mol)? a. ï34 kJ/mol d. ï43 kJ/mol b. ï54 kJ/mol e. ï14 kJ/mol c. ï17 kJ/mol

CAS CH 131 Study Guide - Final Guide: Exothermic Reaction, Endothermic Process, Heat Capacity

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